中文摘要：

以西藏当地推广的油菜代表品种芥菜型油菜（Brassica juncea L.）年河1号、白菜型油菜（Brasscia rapaL.）青油17号和甘蓝型油菜（Brasscia napus L.）藏油5号为材料,设置持续干旱1周和2周的2个干旱处理及干旱后复水1周、2周、3周的3个时期,研究苗期干旱及复水对油菜光合及荧光特性的影响。结果表明：（1）干旱胁迫造成油菜实际光化学效率（ФPSⅡ）、表观光合电子传递速率（ETR）、光化学淬灭系数（qP）、净光合速率（Pn）、气孔导度（Gs）、胞间CO2浓度（Ci）、蒸腾速率（Tr）均下降,且随干旱时间延长而降低。PSⅡ反应中心完全关闭时荧光产量（Fm）、最小荧光（Fo）随干旱时间延长而升高。PSⅡ原初光能转化效率（Fv/Fm）、PSⅡ的潜在活性（Fv/Fo）相对变化小,下降不显著。（2）干旱后复水1～2周时,油菜气体交换参数较前期干旱处理均有升高,复水2周后升高幅度大于1周,尤其是干旱2周处理后复水时参数值大幅度升高;复水3周时,油菜气体交换参数呈下降趋势,净光合速率明显下降。（3）干旱后复水1～2周时,油菜ФPSⅡ、ETR、qP值较对照均有升高,复水1周后较2周后的升高幅度大,尤其是干旱2周处理后复水时,它们的升高幅度大于干旱1周处理后复水的情形;Fm、Fo较对照仍有升高,复水3周各荧光参数值下降。复水后Fv/Fm、Fv/Fo值变化相对较小。

英文摘要：

Effects of drought and rewatering at seedling stage on photosynthesis and chlorophyll fluorescence characteristics were investigated using three Brassica species.They were Brassica juncea L.cv Nianhe 1,Brasscia rapa L.cv Qingyou 17,Brasscia napus L.cv Zangyou 5.Two drought treatments were applied and three rewatering periods were studied.Results indicated that actual photochemical efficiency of PSⅡ,apparent photosynthetic electron transport rate（ETR）,photochemical quenching coefficient（qP）,stomatal conductivity（Gs）,internal CO2 concentration（Ci）,photosynthetic rate（Pn） and transpiration rate（Tr） were decreased under drought.The maximum fluorescence（Fm） and the minimal fluorescence（Fo） were increased under drought.Maximal photochemical efficiency of PSⅡ（Fv/Fm）,potential photochemical efficiency（Fv/Fo） declined.1w and 2w after rewatering,gas exchange parameters were recovered especially on 2w of drought and that after 2w of rewatering.The ФPSⅡ,ETR and qP also increased.The increasing degrees of rewatering was greater both in 2w-drought and 1w-rewatering treatments.Moreover,both Fo and Fm increased after 1w and 2w-rewatering.3w after rewatering,gas exchange parameters and photosynthesis rate decreased.Chlorophyll fluorescence parameters also decreased,but Fv/Fm and Fv/Fo hardly changed.